title: On the nature of gallium species in gallium-modified mordenite and MFI zeolites. A comparative DRIFT study of carbon monoxide adsorption and hydrogen dissociation.
abstract: The results of a DRIFT study of carbon monoxide molecular adsorption and hydrogen dissociative adsorption on gallium-modified mordenite and MFI (ZSM-5) zeolites are presented. It was found that in the reduced gallium-modified mordenite (Ga-MOR) both Ga(3+) and Ga(+) exchanged cations are present and can be detected by CO adsorption. Ga(3+) cations in Ga-MOR dissociatively adsorb molecular hydrogen at elevated temperatures, resulting in the formation of gallium hydride species and acidic hydroxyl groups. In the reduced Ga-MFI evacuated at 823 K under medium vacuum conditions only Ga(+) exchanged intrazeolite cations were detected. It was found, however, that Ga(3+) intrazeolite exchanged cations which form upon high-temperature disproportionation of Ga(+) cations in the reduced Ga-MFI and Ga-MOR can be stabilized by high-temperature oxidation of these zeolites.
authors.affiliation: N.D. Zelinsky Institute of Organic Chemistry of Russian Academy of Sciencie, 47 Leninsky pr., 119991 Moscow, Russia. alexander_serykh@yahoo.com
authors.forename: Alexander I
authors.initials: AI
authors.lastname: Serykh
authors.forename: Stanislav P
authors.initials: SP
authors.lastname: Kolesnikov